Many attempts have been made to provide rigid or substantially rigid airfoils on boats. Among these are U.S. Pat. No. 1,408,868 to Dutcher; U.S. Pat. No. 1,613,890 to Herreshoff; U.S. Pat. No. 3,580,203 to Martin; U.S. Pat. No. 1,700,660 to Williams; and U.S. Pat. No. 3,802,366 to Mankawach. However, in each instance these airfoils are quite complex and therefore, very expensive and have not found practical application on sailing vessels.
As the cost of energy becomes more critical, the need for airfoils which can be used on boats for carrying cargo, as well as on pleasure craft, is increasingly recognized. Therefore, in order to meet this need, it is necessary to provide airfoils which have smooth surfaces to provide laminar airflow and therefore, greater lift. Furthermore, such sails must be adjustable in their contour for different sailing conditions, i.e., depending whether the ship is sailing upwind or downwind. Furthermore, the sail must be rigged so that it can be easily lowered should an unexpected storm arise and means must be provided for reducing air resistance to the minimum around the mast and rigging. Also, it is desirable to have a structure which can be used as a storm sail in severe weather. An ideal is to construct a wind engine that can capture wind energy (from whatever direction) and convert it to propulsive force in the direction wanted--all by remote control.